Rubber composition and tire using same

ABSTRACT

The present invention provides: a rubber composition prepared by mixing 60 to 100 parts by mass of a filler (B), 0.9 to 2.4 parts by mass of a phenol resin (C), 0.07 to 0.2 parts by mass of a methylene donor (D), 1.5 to 2.1 parts by mass of a thiuram based vulcanization accelerating agent (E), and 3.2 to 4.5 parts by mass of a sulfenamide based vulcanization accelerating agent (F), based on 100 parts by mass of the rubber component comprising 20 to 80% by mass of a modified conjugated diene based polymer (A), allowing the ride comfort in normal running to be satisfied in parallel with improvement in the run flat durability (durability in run flat running); and a tire comprising at least one member selected from the group consisting of a side reinforcing rubber layer and a bead filler using the rubber composition.

TECHNICAL FIELD

The present invention relates to a rubber composition capable ofsuppressing the decrease in the elastic modulus at high temperature, anda tire having a side reinforcing rubber layer and/or a bead filler usingthe rubber composition.

BACKGROUND ART

In order to enhance a rigidity of the side wall part of a tire,particularly of a run flat tire, a side reinforcing layer using a rubbercomposition alone or a composite of a rubber composition, a fiber, andthe like, has been conventionally arranged.

For example, in order to secure the run flat durability of the run flattire without damage to the rolling resistance in normal running, a tirehaving a side reinforcing rubber layer and/or a bead filler using arubber composition containing a mixture of a rubber component, 55 partsby mass or more of carbon black based on 100 parts by mass of the rubbercomponent, a phenol resin and a methylene donor (refer to PTL1).

In PTL2, a pneumatic radial tire is proposed, in which a PET with lowthermal shrinkage is used as a carcass reinforcing material to reducesurface irregularities occurring at the roll-up end of the carcass in aside portion, thereby achieving weight reduction and improvedproductivity of the tire.

However, along with improvement in performance of automobiles,particularly of passenger cars, further improvement in the run flatdurability is required.

Furthermore, it is also required to ensure to improve the side cutresistance of tires and the steering stability in normal running,together with the improvement in the run flat durability.

CITATION LIST Patent Literature

PTL1: JP 2010-155550 A

PTL2: JP 2000-301910 A

SUMMARY OF INVENTION Technical Problem

Under the situation described above, an object of the present inventionis to provide a rubber composition allowing the ride comfort in normalrunning to be satisfied in parallel with improvement in the run flatdurability (durability in run flat running), and a tire having at leastone member selected from the group consisting of a side reinforcingrubber layer and a bead filler made thereof, with the improvement in theside cut resistance and the steering stability in normal running of thetire being achieved together with the improvement in the run flatdurability.

Solution to Problem

Intense studies repeated by the present inventors in order to solve theproblem described above have resulted in finding that the problem can besolved by mixing specific amounts of a filler (B), a phenol resin (C), amethylene donor (D), a thiuram based vulcanization accelerating agent(E), and a sulfenamide based vulcanization accelerating agent (F) intothe rubber component of a rubber composition, and, in addition thereto,by allowing the intermediate elongation and the toughness of areinforcing cord of a carcass ply to satisfy a specific relation. Thepresent invention has been completed based on the above knowledge.

In essence, the present invention provides the following [1] to [3].

[1] A rubber composition prepared by mixing 60 to 100 parts by mass of afiller (B), 0.9 to 2.4 parts by mass of a phenol resin (C), 0.07 to 0.2parts by mass of a methylene donor (D), 1.5 to 2.1 parts by mass of athiuram based vulcanization accelerating agent (E), and 3.2 to 4.5 partsby mass of a sulfenamide based vulcanization accelerating agent (F),based on 100 parts by mass of a rubber component comprising 20 to 80% bymass of a modified conjugated diene based polymer (A).

[2] A tire having at least one member selected from the group consistingof a side reinforcing rubber layer and a bead filler using the rubbercomposition according to the above item [1].

[3] The tire according to the above item [2], wherein the tire has, as aframework, a carcass layer comprising at least one carcass ply, areinforcing cord of the carcass ply being an organic fiber cord havingan intermediate elongation of 4.2% or less under a load of 1.5 cN/dtexand a toughness of 45 cN·%/dtex or more.

Advantageous Effects of Invention

According to the present invention, a rubber composition allowing theride comfort in normal running to be satisfied in parallel withimprovement in the run flat durability, and a tire having at least onemember selected from the group consisting of a side reinforcing rubberlayer and a bead filler made thereof, with the improvement in the sidecut resistance and the steering stability in normal running of the tirebeing achieved together with the improvement in the run flat durability.

BRIEF DESCRIPTION OF DRAWING

FIG. 1 is a schematic drawing showing a cross section in one embodimentof the tire of the present invention.

DESCRIPTION OF EMBODIMENT [Rubber Composition]

The rubber composition of the present invention is prepared by mixing 60to 100 parts by mass of a filler (B), 0.9 to 2.4 parts by mass of aphenol resin (C), 0.07 to 0.2 parts by mass of a methylene donor (D),1.5 to 2.1 parts by mass of a thiuram based vulcanization acceleratingagent (E), and 3.2 to 4.5 parts by mass of a sulfenamide basedvulcanization accelerating agent (F), based on 100 parts by mass of arubber component comprising 20 to 80% by mass of a modified conjugateddiene based polymer (A).

The compounding recipe suppresses the decrease in the elastic modulus ofthe rubber composition at high temperature after vulcanization, so thata high elastic modulus is achieved. The high rigidity of the sidereinforcing rubber layer and/or the bead filler can be thereby securedat high temperature (e.g. 180° C.), in parallel with flexibility ataround normal temperature (25° C.) to satisfy the ride comfort in normalrunning.

(Rubber Component)

The rubber component of the rubber composition of the present inventionneeds to comprise 20 to 80% by mass of a modified conjugated diene basedpolymer (A). The modified conjugated diene based polymer (A) of therubber composition of the present invention may be used singly or incombination of two or more. With a content of the modified conjugateddiene based polymer (A) of 20% by mass or more in the rubber component,reduction in heat generation is achieved, so that the run flatdurability can be improved. From this viewpoint, the content of themodified conjugated diene based polymer (A) is still more preferably 40%by mass or more.

As the modified conjugated diene based polymer (A), those containingamine-modified conjugated diene based polymer can be preferably used toobtain a rubber composition which achieves reduction in heat generation,so that a tire having further improved run flat durability can be madetherefrom.

Preferred examples of the amine-modified conjugated diene based polymerinclude ones having a primary amino group protected with a removablegroup or a secondary amino group protected with a removable group as anamine functional group for modification introduced in the molecule, andones having a silicon atom-containing functional group furtherintroduced in the molecule.

Examples of the primary amino group protected with a removable group(also referred to as a protected primary amino group) include aN,N-bis(trimethylsilyl)amino group, and examples of the secondary aminogroup protected with a removable group include aN,N-(trimethylsilyl)alkylamino group. The N,N-(trimethylsilyl)alkylaminogroup-containing group may be any of a non-cyclic residue and a cyclicresidue.

Among the amine-modified conjugated diene based polymers describedabove, a primary amine-modified conjugated diene based polymer modifiedwith a protected primary amino group is more suitably used.

Examples of the silicon atom-containing functional group include ahydrocarbyloxy silyl group and/or a silanol group comprising a siliconatom to which a hydrocarbyloxy group and/or a hydroxy group bonded.

Such a functional group for modification may be present at any of thepolymerization initiation end, the side chain, and the activepolymerization end of a conjugated diene based polymer. In the presentinvention, the functional group has an amino group protected with aremovable group and at least one (e.g. one or two) silicon atom to whicha hydrocarbyloxy group and a hydroxyl group are bonded, preferably atthe polymerization end, more preferably at the same activepolymerization end.

<Conjugated Diene Based Polymer>

The conjugated diene based polymer used for modification may be ahomopolymer of conjugated diene compound, a copolymer of two or moreconjugated diene compounds, or a copolymer of a conjugated dienecompound and an aromatic vinyl compound.

The conjugate diene compound described above includes, for example,1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene,2-phenyl-1,3-butadiene, 1,3-hexadiene and the like. They may be usedalone or in combination of two or more kinds thereof, and among them,1,3-pentadiene is particularly preferred.

The aromatic vinyl compound used for copolymerization with the conjugatediene compound includes, for example, styrene, α-methylstyrene,1-vinylnaphthalene, 3-vinyltoluene, ethylvinylbenzene, divinylbenzene,4-cyclohexylstyrene, 2,4,6-trimethylstyrene and the like. They may beused alone or in combination of two or more kinds thereof, and amongthem, styrene is particularly preferred.

As the conjugated diene based copolymer, at least one conjugated dienebased copolymer selected from the group consisting of polybutadiene,polyisoprene, an isoprene-butadiene copolymer, an ethylene-butadienecopolymer, a propylene-butadiene copolymer and a styrene-butadienecopolymer is preferred, and polybutadiene is particularly preferred.

In order to react an active end of the conjugate diene based polymerwith protected primary amine to modify it, the above conjugate dienebased polymer is preferably provided with a living property or apseudo-living property in at least 10% of a polymer chain.Polymerization reaction providing the above living property includesreaction in which a conjugate diene compound alone or a conjugate dienecompound and an aromatic vinyl compound are subjected to anionicpolymerization in an organic solvent using an organic alkali metalcompound as an initiator or reaction in which a conjugate diene compoundalone or a conjugate diene compound and an aromatic vinyl compound aresubjected to coordinate anionic polymerization in an organic solvent bya catalyst containing a lanthanum series rare earth element compound.The former is preferred since it can provide a polymer having a highcontent of a vinyl bond in a conjugate diene part as compared with thatin the latter. The heat resistance can be improved by enhancing thevinyl bond amount.

The organic alkali metal compound used as the initiator for the anionicpolymerization described above is preferably an organic lithiumcompound. The organic lithium compound shall not specifically berestricted, and hydrocarbyllithium and lithium amide compounds arepreferably used. When hydrocarbyllithium of the former is used, aconjugate diene based polymer which has a hydrocarbyl group at apolymerization initiation end and in which the other end is apolymerization active site is obtained. Also, when the lithium amidecompound of the latter is used, a conjugate diene based polymer whichhas a nitrogen-containing group at a polymerization initiation end andin which the other end is a polymerization active site is obtained.

The hydrocarbyllithium described above is preferably a product having ahydrocarbyl group having 2 to 20 carbon atoms, and it includes, forexample, ethyllithium, n-propyllithium, isopropyllithium,n-butyllithium, sec-butyllithium, tert-octyllithium, n-decyllithium,phenyllithium, 2-naphthyllithium, 2-butylphenyllithium,4-phenylbutyllithium, cyclohexyllithium, cyclopentyllithium and reactionproducts of diisopropenylbenzene and butyllithium. Among them,n-butyllithium is particularly suited.

On the other hand, the lithium amide compound includes, for example,lithium hexamethyleneimide, lithium pyrrolidide, lithium piperidide,lithium heptamethyleneimide, lithium dodecamethyleneimide, lithiumdimethylamide, lithium diethylamide, lithium dibutylamide, lithiumdipropylamide, lithium diheptylamide, lithium dihexylamide, lithiumdioctylamide, lithium di-2-ethylhexylamide, lithium didecylamide,lithium N-methylpiperazide, lithium ethylpropylamide, lithiumethylbutylamide, lithium ethylbenzylamide, lithium methylphenethylamideand the like. Among them, cyclic lithium amide such as lithiumhexamethyleneimide, lithium pyrrolidide, lithium piperidide, lithiumheptamethyleneimide, lithium dodecamethyleneimide and the like arepreferred from the viewpoints of an interaction effect to carbon blackand a polymerization initiation ability, and lithium hexamethyleneimideand lithium pyrrolidide are particularly suited.

In general, compounds prepared in advance from secondary amines andlithium compounds can be used for the above lithium amide compounds, andthey can be prepared as well in the polymerization system (in-Situ).Also, a use amount of the above polymerization initiator is selectedpreferably in a range of 0.2 to 20 millimole per 100 g of the monomer.

A method for producing the conjugate diene based polymer by the anionicpolymerization using the organic lithium compounds described above asthe polymerization initiator shall not specifically be restricted, andmethods which have so far been publicly known can be used.

To be specific, the conjugate diene compound or the conjugate dienecompound and the organic vinyl compound are subjected to anionicpolymerization in the organic solvent which is inactive to the reaction,for example, a hydrocarbon based solvent such as aliphatic, alicyclicand aromatic hydrocarbon compounds using the lithium compounds describedabove as the polymerization initiator under the presence of a randomizerused if desired, whereby the targeted conjugate diene based polymerhaving an active end is obtained.

Further, when the organic lithium compounds is used as thepolymerization initiator, not only the conjugate diene based polymerhaving an active end but also the copolymer of the conjugate dienecompound and the organic vinyl compound which has an active end canefficiently be obtained as compared with a case where the catalystcontaining the lanthanum based rear earth element compound describedabove is used.

The hydrocarbon base solvent described above is preferably hydrocarbonshaving 3 to 8 carbon atoms, and capable of being listed are, forexample, propane, n-butane, isobutane, n-pentane, isopentane, n-hexane,cyclohexane, propene, 1-butene, isobutene, trans-2-butene, cis-2-butene,1-pentene, 2-pentene, 1-hexene, 2-hexene, benzene, toluene, xylene,ethylbenzene and the like. They may be used alone or in a mixture of twoor more kinds thereof.

A concentration of the monomer in the solvent is preferably 5 to 50% bymass, more preferably 10 to 30% by mass. When the conjugate dienecompound and the aromatic vinyl compound are used to copolymerize them,a content of the organic vinyl compound in the charged monomer mixturefalls preferably in a range of 55% by mass or less.

The randomizer used if desired is a compound having actions such ascontrolling of a micro structure of the conjugate diene based polymer,for example, an increase in a 1,2-bond of a butadiene part in abutadiene-styrene copolymer and a 3,4-bond in an isoprene polymer,controlling of a composition distribution of a monomer unit in aconjugate diene compound-aromatic vinyl compound copolymer, for example,randomization of a butadiene unit and a styrene unit in abutadiene-styrene copolymer. The above randomizer shall not specificallybe restricted, and optional compounds suitably selected from publiclyknown compounds usually used as a randomizer can be used. To bespecific, capable of being listed are ethers and tertiary amines such asdimethoxybenzene, tetrahydrofuran, dimethoxyethane, diethylene glycoldibutyl ether, diethylene glycol dimethyl ether, oxolanylpropaneoligomers (particularly oligomers containing2,2-bis(2-tetrahydrofuryl)-propane), triethylamine, pyridine,N-methylmorpholine, N,N,N′,N′-tetramethylethylenediamine,1,2-piperidinoethane and the like. Further, potassium salts such aspotassium tert-amylate, potassium tert-butoxide and the like and sodiumsalts such as sodium tert-amylate and the like can be used as well.

The above randomizers may be used alone or in combination of two or morekinds thereof. A use amount thereof is selected preferably in a range of0.01 to 1000 mole equivalent per mole of the lithium compound.

Temperature in the above polymerization reaction is selected in a rangeof preferably 0 to 150° C., more preferably 20 to 130° C. Thepolymerization reaction can be carried out under pressure generated, andusually, it is operated preferably at pressure which is sufficient formaintaining the monomer substantially in a liquid phase. That is, thoughdepending on the respective materials subjected to the polymerization,the polymerization medium used and the polymerization temperature, thehigher pressure can be used if desired, and the above pressure can beobtained by a suitable method such as applying pressure to the reactorby gas which is inert to the polymerization reaction.

<Modifying Agent>

In the present invention, the reaction of the active end of a conjugateddiene based polymer having the active end obtained as described abovewith a protected primary amine compound as a modifier enablesmanufacturing of a primary amine-modified conjugated diene basedpolymer, and the reaction with a protected secondary amine compoundenables manufacturing of a secondary amine-modified conjugated dienebased polymer. As the protected primary amine compound, an alkoxysilanecompound having a protected primary amine group is suitably used, and asthe protected secondary amine compound, an alkoxysilane compound havinga protected secondary amine group is suitably used.

The alkoxysilane compounds having a protected primary amino group whichare used as the above modifying agent include, for example,N,N-bis(trimethylsilyl)aminopropylmethyldimethoxysilane,1-trimethylsilyl-2,2-dimethoxy-1-aza-2-silacyclopentane,N,N-bis(trimethylsilyl)aminopropylmethyltrimethoxysilane,N,N-bis(trimethylsilyl)aminopropylmethyltriethoxysilane,N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane,N,N-bis(trimethylsilyl)aminoethyltrimethoxysilane,N,N-bis(trimethylsilyl)aminoethyltriethoxysilane,N,N-bis(trimethylsilyl)aminoethylmethyldimethoxysilane,N,N-bis(trimethylsilyl)aminoethylmethyldiethoxysilane and the like, andthey are preferablyN,N-bis(trimethylsilyl)aminopropylmethyldimethoxysilane,N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane or1-trimethylsilyl-2,2-dimethoxy-1-aza-2-silacyclopentane.

Further, the modifying agents include as well alkoxysilane compoundshaving a protected secondary amino group such asN-methyl-N-trimethylsilylaminopropyl(methyl)dimethoxysilane,N-methyl-N-trimethylsilylaminopropyl(methyl)diethoxysilane,N-trimethylsilyl(hexamethyleneimine-2-yl)propyl(methyl)dimethoxysilane,N-trimethylsilyl(hexamethyleneimine-2-yl)propyl(methyl)diethoxysilane,N-trimethylsilyl(pyrrolidine-2-yl)propyl(methyl)dimethoxysilane,N-trimethylsilyl(pyrrolidine-2-yl)propyl(methyl)diethoxysil ane,N-trimethylsilyl(piperidine-2-yl)propyl(methyl)dimethoxysilane,N-trimethylsilyl(piperidine-2-yl)propyl(methyl)diethoxysilane,N-trimethylsilyl(imidazole-2-yl)propyl(methyl)dimethoxysilane,N-trimethylsilyl(imidazole-2-yl)propyl(methyl)diethoxysilane,N-trimethylsilyl(4,5-dihydroimidazole-5-yl)propyl(methyl)dimethoxysilane,N-trimethylsilyl(4,5-dihydroimidazole-5-yl)propyl(methyl)diethoxysilaneand the like; alkoxysilane compounds having an imino group such asN-(1,3-dimethylbutylidene)-3-(triethoxysilyl)-1-propaneamine,N-(1-methylethylidene)-3-(triethoxysilyl)-1-propaneamine,N-ethylidene-3-(triethoxysilyl)-1-propaneamine,N-(1-methylpropylidene)-3-(triethoxysilyl)-1-propaneamine,N-(4-N,N-dimthylaminobenzylidene)-3-(triethoxysilyl)-1-propaneamine,N-(cyclohexylidene)-3-(triethoxysilyl)-1-propaneamine and the like;alkoxysilane compounds having an amino group such as3-dimethylaminopropyl(triethoxy)silane,3-dimethylaminopropyl(trimethoxy)silane,3-diethylaminopropyl(triethoxy)silane,3-diethylaminopropyl(trimethoxy)silane,2-dimethylaminoethyl(triethoxy)silane,2-dimethylaminoethyl(trimethoxy)silane,3-dimethylaminopropyl(diethoxy)methylsilane,3-dibutylaminopropyl(triethoxy)silane and the like.

The above modifying agents may be used alone or in combination of two ormore kinds thereof. Also, the above modifying agents may be partialcondensation products.

In this connection, the partial condensation products mean the modifyingagents in which a part (not all) of SiOR is converted into a SiOSi bondby condensation.

In modifying reaction carried out by the modifying agent describedabove, a use amount of the above modifying agent is preferably 0.5 to200 mmol/kg·conjugate diene based polymer. The above use amount is morepreferably 1 to 100 mmol/kg·conjugate diene based polymer, particularlypreferably 2 to 50 mmol/kg·conjugate diene based polymer. In thisregard, the conjugate diene based polymer means a mass of the polymeralone which does not contain additives such as an antioxidant and thelike added in the production or after the production. Controlling a useamount of the modifying agent to the ranges described above makes afiller, particularly carbon black excellent in a dispersibility andallows the rapture characteristic and the low heat generation propertyafter vulcanization to be improved.

An adding method of the modifying agents described above shall notspecifically be restricted and includes a method in which they are addedin one lot, a method in which they are added in a divided lot, a methodin which they are added continuously and the like, and the method inwhich they are added in one lot is preferred.

Also, the modifying agent can be bonded to any of a principal chain anda side chain of the polymer in addition to a polymerization initiatingend and a polymerization finishing end thereof, and it is introducedpreferably into the polymerization initiating end or the polymerizationfinishing end from the viewpoint that energy can be inhibited fromdisappearing from an end of the polymer to improve the low heatgeneration property.

<Condensation Accelerator>

In the present invention, a condensation accelerator is preferably usedin order to accelerate condensation reaction in which the alkoxysilanecompound having a protected primary amino group used as the modifyingagent described above participates.

Capable of being used as the above condensation accelerator arecompounds having a tertiary amino group or organic compounds having atleast one element belonging to any of a 3rd group, a 4th group, a 5thgroup, a 12th group, a 13th group, a 14th group and a 15th group in theperiodic table (long periodic table). Further, the condensationaccelerator is preferably alkoxides, carboxylates or acetylacetonatecomplex salts containing at least one metal selected from the groupconsisting of titanium (Ti), zirconium (Zr), bismuth (Bi), aluminum (Al)and tin (Sn).

The condensation accelerator used above can be added before themodification reaction described above, but it is preferably added to themodification reaction system in the middle of the modification reactionand/or after finishing it. When it is added before the modificationreaction, it is reacted directly with the active end, and thehydrocarbyloxy group having a protected primary amino group is notintroduced into the active end in a certain case.

An addition timing of the condensation accelerator is usually after 5minutes to 5 hours since initiating the modification reaction,preferably after 15 minutes to 1 hour since initiating the modificationreaction.

Capable of being listed as the condensation accelerator are, to bespecific, compounds containing titanium, such as tetramethoxytitanium,tetraethoxytitanium, tetra-n-propoxytitanium, tetraisopropoxytitanium,tetra-n-butoxytitanium, tetra-n-butoxytitanium oligomers,tetra-sec-butoxytitanium, tetra-tert-butoxytitanium,tetra(2-ethylhexyl)titanium,bis(octanedioleate)bis(2-ethylhexyl)titanium,tetra(octanedioleate)titanium, titanium lactate, titaniumdipropoxybis(triethanolaminate), titaniumdibutoxybis(triethanolaminate), titanium tributoxystearate, titaniumtripropoxystearate, titanium ethylhexyltholeate, titaniumtripropoxyacetylacetonate, titanium dipropoxybis(acetylacetonate),titanium tripropoxyethylacetoacetate, titaniumpropoxyacetylacetonatebis(ethylacetoacetate), titaniumtributoxyacetylacetonate, titanium dibutoxybis(acetylacetonate),titanium tributoxyethylacetoacetate, titaniumbutoxyacetylacetonatebis(ethylacetoacetate), titaniumtetrakis(acetylacetonate), titaniumdiacetylacetonatebis(ethylacetoacetate), bis(2-ethylhexanoate)titaniumoxide, bis(laurate)titanium oxide, bis(naphthenate)titanium oxide,bis(stearate)titanium oxide, bis(oleate)titanium oxide,bis(linoleate)titanium oxide, tetrakis(2-ethylhexanoate)titanium,tetrakis(laurate)titanium, tetrakis(naphthenate)titanium,tetrakis(stearate)titanium, tetrakis(oleate)titanium,tetrakis(linoleate)titanium and the like.

Further, capable of being listed as the condensation accelerator are,for example, tris(2-ethylhexanoate)bismuth, tris(laurate)bismuth,tris(naphthenate)bismuth, tris(stearate)bismuth, tris(oleate)bismuth,tris(linoleate)bismuth, tetraethoxyzirconium, tetra-n-propoxyzirconium,tetraisopropoxyzirconium, tetra-n-butoxyzirconium,tetra-sec-butoxyzirconium, tetra-tert-butoxyzirconium,tetra(2-ethylhexyl)zirconium, zirconium tributoxystearate, zirconiumtributoxyacetylacetonate, zirconium dibutoxybis(acetylacetonate),zirconium tributoxyethylacetoacetate, zirconiumbutoxyacetylacetonatebis(ethylacetoacetate), zirconiumtetrakis(acetylacetonate), zirconiumdiacetylacetonatebis(ethylacetoacetate), bis(2-ethylhexanoate)zirconiumoxide, bis(laurate)zirconium oxide, bis(naphthenate)zirconium oxide,bis(stearate)zirconium oxide, bis(oleate)zirconium oxide,bis(linoleate)zirconium oxide, tetrakis(2-ethylhexanoate)zirconium,tetrakis(laurate)zirconium, tetrakis(naphthenate)zirconium,tetrakis(stearate)zirconium, tetrakis(oleate)zirconium,tetrakis(linoleate)zirconium and the like.

Further, capable of being listed are triethoxyaluminum,tri-n-propoxyaluminum, triisopropoxyaluminum, tri-n-butoxyaluminum,tri-sec-butoxyaluminum, tri-tert-butoxyaluminum,tri(2-ethylhexyl)aluminum, aluminum dibutoxystearate, aluminumdibutoxyacetylacetonate, aluminum butoxybis(acetylacetonate), aluminumdibutoxyethylacetoacetate, aluminum tris(acetylacetonate), aluminumtris(ethylacetoacetate), tris(2-ethylhexanoate)aluminum,tris(laurate)aluminum, tris(naphthenate)aluminum,tris(stearate)aluminum, tris(oleate)aluminum, tris(linoleate)aluminumand the like.

Among the condensation accelerators described above, the titaniumcompounds are preferred, and the alkoxides of titanium metal, thecarboxylates of titanium metal or the acetylacetonate complex salts oftitanium metal are particularly preferred.

A use amount of the above condensation accelerators is preferably 0.1 to10, particularly preferably 0.5 to 5 in terms of a mole ratio of a molenumber of the compounds described above to a whole mole number of thehydrocarbyloxy groups present in the reaction system. The condensationreaction is efficiently promoted by controlling a use amount of thecondensation accelerators to the ranges described above.

The condensation reaction time is usually 5 minutes to 10 hours,preferably 15 minutes to 5 hours. Controlling the condensation reactiontime to the ranges described above makes it possible to completesmoothly the condensation reaction.

A pressure of the reaction system in the condensation reaction isusually 0.01 to 20 MPa, preferably 0.05 to 10 MPa.

<(A) Modified Conjugate Diene Based Polymer>

(A) The modified conjugate diene based polymer obtained in the mannerdescribed above has a Mooney viscosity (ML₁₊₄, 100° C.) of preferably 10to 150, more preferably 15 to 100. When the Mooney viscosity is lessthan 10, the rubber physical properties including the rupture resistantcharacteristic are not sufficiently obtained, and when it exceeds 150,the operability is inferior to make it difficult to mix the polymer withthe compounding agents.

Also, the non-vulcanized rubber composition according to the presentinvention which is mixed with (A) the modified conjugate diene basedpolymer described above has a Mooney viscosity (ML₁₊₄, 130° C.) ofpreferably 10 to 150, more preferably 30 to 100.

In (A) the modified conjugate diene based polymer used for the rubbercomposition of the present invention, a ratio (Mw/Mn) of a weightaverage molecular weight (Mw) to a number average molecular weight (Mn),that is, a molecular weight distribution (Mw/Mn) is preferably 1 to 3,more preferably 1.1 to 2.7.

Controlling a molecular weight distribution (Mw/Mn) of (A) the modifiedconjugate diene based polymer within the ranges described above makes iteasy to knead them without reducing an operability of the rubbercomposition when mixing the modified conjugate diene based polymer withthe rubber composition and makes it possible to enhance sufficiently thephysical properties of the rubber composition.

Further, (A) the modified conjugate diene based polymer used for therubber composition of the present invention has a number averagemolecular weight (Mn) of preferably 100,000 to 500,000, more preferably150,000 to 300,000. Controlling a number average molecular weight of (A)the modified conjugate diene based polymer within the ranges describedabove inhibits a reduction in an elastic modulus of the vulcanizedmatter and an elevation in the hysteresis loss to obtain the excellentrupture resistant characteristic and provides the rubber compositioncontaining (A) the above modified conjugate diene based polymer with anexcellent kneading operability.

From the viewpoint of further reduction in heat generation, the modifiedconjugated diene based polymer (A) for use in the rubber composition ofthe present invention is preferably an amine-modified polybutadiene,more preferably a primary amine-modified polybutadiene or a secondaryamine-modified polybutadiene, and particularly preferably a primaryamine-modified polybutadiene.

The modified conjugated diene based polymer (A) of the present inventionhas a vinyl bond content in the butadiene portion of preferably 10% to60% by mass, more preferably 12% to 60% by mass, an Mw of preferably100,000 to 500,000, an Mw/Mn of preferably 2 or less, and a primaryamino group content of preferably 2.0 to 10.0 mmol/kg.

<Other Rubber Components>

Among the rubber components of the present invention, examples of theother components used in combination with the modified conjugated dienebased polymer (A) include natural rubber and at least one diene basedrubber selected from synthetic diene based rubbers other than themodified conjugated diene based polymer (A), of which the content ispreferably 80 to 20% by mass to balance 20 to 80% by mass of themodified conjugated diene based polymer (A) in the rubber component. Acontent of the other rubber components of 60 to 20% by mass is morepreferred to balance 40 to 80% by mass of the modified conjugated dienebased polymer (A) in the rubber component.

Examples of the synthetic diene based rubber described above include astyrene-butadiene copolymer (SBR), polybutadiene (BR), polyisoprene(IR), a styrene-isoprene copolymer (SIR), an ethylene-butadienecopolymer (EBR), a propylene-butadiene copolymer (PBR), butyl rubber(IIR), halogenated butyl rubber, an ethylene-propylene-diene terpolymer(EPDM) and a mixture thereof. A part or all of the other diene basedsynthetic rubbers is more preferably a diene based modified rubber whichis provided with a branched structure by using a multifunctionalmodifying agent, for example, a modifying agent such as zinctetrachloride.

(Filler (B))

In the rubber composition of the present invention, the content offiller as component (B) needs to be 60 to 100 parts by mass, based on100 parts by mass of the rubber component. With a content of the filler(B) of less than 60 parts by mass, the vulcanized rubber properties ofthe rubber composition obtained allow insufficient reinforcing effect tobe exhibited. With a content of the filler (B) of more than 100 parts bymass, for example, the loss tangent tan δ (at 25° C.) in the vulcanizedrubber properties of the rubber composition obtained increases, so thatlower fuel consumption (reduction in heat generation) in normal runningcannot be achieved due to an increased rolling resistance.

As the filler (B) in the present invention, an inorganic filler such ascarbon black and silica is used. The filler (B) containing 50% by massor more of carbon black and 50% by mass or less of silica is preferred,and the filler (B) of carbon black alone is more preferred.

In order to allow the rubber composition obtained to satisfy thevulcanized rubber physical properties described above, the carbon blackused in the rubber composition of the present invention is preferablyone selected from the group consisting of an FEF grade, an FF grade, anHAF grade, N339, an IISAF grade, an ISAF grade, and an SAF grade; and anFEF grade is particularly preferred.

As the silica, silica by wet method, silica by dry method and colloidalsilica are preferred and silica by wet method is particularly preferred,though not specifically limited. One type of silica may be used alone,or two or more types of silica may be mixed for use.

(Phenol Resin (C))

Examples of the phenol resin (C) for use in the present inventioninclude a novolac-type phenol resin, a novolac-type cresol resin, anovolac-type xylenol resin, a novolac-type resorcinol resin, and anoil-modified resin therefrom, and preferably at least one of the resinsis used.

Examples of the oil used in oil modification of the phenolic resininclude rosin oil, tall oil, cashew oil, linoleic oil, oleic acid, andlinolenic acid, and preferably at least one of these oils is used. Fromthe viewpoint of achieving both of the run flat durability and the ridecomfort, the cashew oil modification is preferred.

The amount of the phenol resin mixed in 100 parts by mass of the rubbercomponent is 0.9 to 2.4 parts by mass. With an amount of the phenolresin mixed of 0.9 parts by mass or more, the rubber composition canhave a higher elastic modulus after vulcanization, and the unvulcanizedrubber composition can have improved workability. On the other hand,with an amount of the phenol resin mixed of 2.4 parts by mass or less,the loss of flexibility of the rubber composition after vulcanizationcan be inhibited.

In the rubber composition of the present invention, preferably theamounts of the filler (B) and the phenol resin (C) mixed (parts by mass)satisfy the following Expression:

1.0≦[mass ratio {amount of phenol resin (C) mixed/amount of carbon black(B) mixed}]×100≦4.0.

With [mass ratio {amount of phenol resin (C) mixed/amount of carbonblack (B) mixed}]×100 of 1.0 or more, the elastic modulus at hightemperature (e.g. 180° C.) is relatively high as compared to the elasticmodulus at around normal temperature (25° C.), resulting in preferredimprovement in the run flat durability. With a mass ratio of 4.0 orless, the preferred flexibility at around normal temperature (25° C.)tends to be secured.

(Methylene Donor (D))

The methylene donor (D) in the present invention is used as curing agentof the phenol resin (C), and preferred examples thereof include at leastone selected from the group consisting of hexamethylenetetramine,hexamethoxymethylmelamine, paraformaldehyde, acetaldehyde ammonia,α-polyoxymethylene, a polyvalent methylolmelamine derivative, anoxazolidine derivative, and a polyvalent methylolated acetylene urea.Among them, at least one selected from the group consisting ofhexamethylenetetramine and hexamethoxymethylmelamine is more preferredfrom the viewpoint of obtaining a rubber composition having a highercuring rate and a higher elastic modulus.

Based on 100 parts by mass of the rubber component, the amount of amethylene donor (D) mixed is 0.07 to 0.2 parts by mass. With an amountof the methylene donor mixed in the range, the phenol resin can besecurely cured without negative influence on the cross-linking system ofrubber. From the viewpoint of achieving both of the run flat durabilityand the ride comfort, the amount to be mixed is preferably 0.08 to 0.18parts by mass. From this viewpoint, based on 100 parts by mass of thephenol resin (C), the amount of the methylene donor (D) mixed ispreferably 3 to 80 parts by mass, more preferably 5 to 80 parts by mass,still more preferably 5 to 50 parts by mass, furthermore preferably 5 to30 parts by mass, and particularly preferably 5 to 20 parts by mass.

(Thiuram Based Vulcanization Accelerating Agent (E) and SulfenamideBased Vulcanization Accelerating Agent (F))

As the vulcanization accelerating agents in the rubber composition ofthe present invention, it is important to use a thiuram basedvulcanization accelerating agent (E) in combination with a sulfenamidebased vulcanization accelerating agent (F). The combination of a thiurambased vulcanization accelerating agent (E) and a sulfenamide basedvulcanization accelerating agent (F) allows the rubber composition tohave a higher elastic modulus at high temperature (e.g. 180° C.) aftervulcanization and achieve further reduction in the heat generation(lower fuel consumption) after vulcanization. By the application of therubber composition having a higher elastic modulus at high temperatureto the side reinforcing rubber of a tire, the deflection of the tiresidewall can be suppressed. By the application of the rubber compositionto the side reinforcing rubber of a tire, further reduction in the heatgeneration can be achieved, so that the heat generation of the tire inrun flat running can be suppressed and the rolling resistance of thetire in normal running can be reduced.

From the viewpoints described above, preferably the amounts of a thiurambased vulcanization accelerating agent (E) and a sulfenamide basedvulcanization accelerating agent (F) mixed (parts by mass) satisfy thefollowing Expression (I).

0.45≦mass ratio [amount of thiuram based vulcanization acceleratingagent (E) mixed/amount of sulfenamide based vulcanization acceleratingagent (F) mixed]≦0.65   (I)

With [amount of thiuram based vulcanization accelerating agent (E)mixed/amount of sulfenamide based vulcanization accelerating agent (F)mixed] of 0.45 or more, the elastic modulus at high temperature (e.g.180° C.) is relatively high as compared to the elastic modulus at aroundnormal temperature (25° C.), resulting in preferred improvement in therun flat durability. With a mass ratio of 0.65 or less, rubber scorchinghardly occurs in processing of unvulcanized rubber composition,resulting in preferred improvement in the workability of unvulcanizedrubber.

<Thiuram Based Vulcanization Accelerating Agent (E)>

In the rubber composition of the present invention, the amount of athiuram based vulcanization accelerating agent (E) mixed is 1.5 to 2.1parts by mass based on 100 parts by mass of the rubber component. Withinthe mixing range, the effect of use in combination with a sulfenamidebased vulcanization accelerating agent (F) can be enhanced.

Examples of the thiuram based vulcanization accelerating agent (E) ofthe present invention include tetrakis(2-ethylhexyl)thiuram disulfide,tetramethylthiuram disulfide, tetraethylthiuram disulfide,tetrapropylthiuram disulfide, tetraisopropylthiuram disulfide,tetrabutylthiuram disulfide, tetrapentylthiuram disulfide,tetrahexylthiuram disulfide, tetraheptylthiuram disulfide,tetraoctylthiuram disulfide, tetranonylthiuram disulfide,tetradecylthiuram disulfide, tetradodecylthiuram disulfide,tetrastearylthiuram disulfide, tetrabenzylthiuram disulfide,tetramethylthiuram monosulfide, tetraethylthiuram monosulfide,tetrapropylthiuram monosulfide, tetraisopropylthiuram monosulfide,tetrabutylthiuram monosulfide, tetrap entylthiuram monosulfide,tetrahexylthiuram monosulfide, tetraheptylthiuram monosulfide,tetraoctylthiuram monosulfide, tetranonylthiuram monosulfide,tetradecylthiuram monosulfide, tetradodecylthiuram monosulfide,tetrastearylthiuram monosulfide, tetrabenzylthiuram monosulfide, anddipentamethylenethiuram tetrasulfide. Among these,tetrakis(2-ethylhexyl)thiuram disulfide and tetrabenzylthiuram disulfideare preferred due to easy control of the vulcanization rate.

<Sulfenamide Based Vulcanization Accelerating Agent (F)>

In the rubber composition of the present invention, the amount of asulfenamide based vulcanization accelerating agent (F) mixed is 3.2 to4.5 parts by mass based on 100 parts by mass of the rubber component.Within the mixing range, the effect of use in combination with thethiuram based vulcanization accelerating agent (E) can be enhanced.

By increasing the amounts of a thiuram based vulcanization acceleratingagent (E) and a sulfenamide vulcanization accelerating agent (F) as thevulcanization accelerating agents of the present invention as describedabove, the elastic modulus at high temperature (e.g. 180° C.) of therubber composition after vulcanization can be further increased, andfurther reduction in the heat generation (lower fuel consumption) of therubber composition after vulcanization can be achieved.

Examples of the sulfenamide based vulcanization accelerating agent (F)of the present invention include N-cyclohexyl-2-benzothiazolylsulfenamide, N,N-dicyclohexyl-2-benzothiazolyl sulfenamide, N-tert-butyl-2-benzothiazolyl sulfenamide, N-oxydiethylene-2-benzothiazolylsulfenamide, N-methyl-2-benzothiazolyl sulfenamide,N-ethyl-2-benzothiazolyl sulfenamide, N-propyl-2-benzothiazolylsulfenamide, N-butyl-2-benzothiazolyl sulfenamide,N-pentyl-2-benzothiazolyl sulfenamide, N-hexyl-2-benzothiazolylsulfenamide, N-pentyl-2-benzothiazolyl sulfenamide,N-octyl-2-benzothiazolyl sulfenamide, N-2-ethylhexyl-2-benzothiazolylsulfenamide, N-decyl-2-benzothiazolyl sulfenamide,N-dodecyl-2-benzothiazolyl sulfenamide, N-stearyl-2-benzothiazolylsulfenamide, N,N-dimethyl-2-benzothiazolyl sulfenamide,N,N-diethyl-2-benzothiazolyl sulfenamide, N,N-dipropyl-2-benzothiazolylsulfenamide, N,N-dibutyl-2-benzothiazolyl sulfenamide,N,N-dipentyl-2-benzothiazolyl sulfenamide, N,N-dihexyl-2-benzothiazolylsulfenamide, N,N-dipentyl-2-benzothiazolyl sulfenamide,N,N-dioctyl-2-benzothiazolyl sulfenamide amide,N,N-di-2-ethylhexyl-benzothiazolyl sulfenamide, N-decyl-2-benzothiazolylsulfenamide, N,N-didodecyl-2-benzothiazolyl sulfenamide, andN,N-distearyl-2-benzothiazolyl sulfenamide. Among these,N-cyclohexyl-2-benzothiazolyl sulfenamide, N-tert-butyl-2-benzothiazolylsulfenamide and N,N-dicyclohexyl-2-benzothiazolyl sulfenamide arepreferred due to easy control of the vulcanization rate.

(Vulcanizing Agent)

Preferred examples of the vulcanizing agent of the present inventioninclude at least one sulfur-containing vulcanizing agent selected fromthe group consisting of sulfur and sulfur donors, and the amount thereofmixed into 100 parts by mass of the rubber component is preferably 1.0to 10.0 parts by mass in terms of a sulfur content, more preferably 2.0to 10.0 parts by mass in terms of a sulfur content, and particularlypreferably 2.0 to 8.0 parts by mass in terms of a sulfur content. With asulfur content of 1.0 part by mass or more, the rupture strength,abrasion resistance and reduction in heat generation of the rubbercomposition after vulcanization are improved. With a sulfur content of10.0 parts by mass or less, the rubber elasticity can be secured.

(Other Compounding Agent)

The rubber composition of the present invention may further containvarious optional chemicals usually used in the rubber industry such asan antioxidant, a scorch inhibitor, zinc oxide, stearic acid and aprocess oil, within a range in which the effects of the presentinvention are not damaged.

Examples of the antioxidant for use in the rubber composition of thepresent invention include a 2,2,4-trimethyl-1,2-dihydroquinolinepolymer, AW (6-ethoxy-1,2-dihydro-2,2,4-trimethylquinoline), ahigh-temperature condensate of diphenylamine and acetone, 6C[N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine], and 3C(N-isopropyl-N′-phenyl-p-phenylenediamine). The amount thereof used ispreferably 0.1 to 5.0 parts by mass, and more preferably 0.3 to 3.0parts by mass based on 100 parts by mass of the rubber component.

As described above, it is important to control the amount of eachcompounding material mixed within an appropriate range for highlyachieving both of the run flat durability and the riding comfort. It is,however, not sufficient to optimize the amount of the individualmaterials mixed only. It is important to control the balance of theamount of each material mixed within a specific range for achieving bothof the high run flat durability and the riding comfort.

In other words, the outstanding effect of the rubber composition can beproduced by mixing 60 to 100 parts by mass of a filler, 0.9 to 2.4 partsby mass of a phenol resin, 0.07 to 0.2 parts by mass of a methylenedonor, 1.5 to 2.1 parts by mass of a thiuram based vulcanizationaccelerating agent, 3.2 to 4.5 parts by mass of a sulfenamide basedvulcanization accelerating agent into 100 parts by mass of a rubbercomponent comprising 20 to 80% by mass of a modified conjugated dienebased polymer. The effect cannot be obtained based on the individualevaluation of the mixed materials.

(Tire)

The tire of the present invention is described as follows with referenceto drawing. FIG. 1 is a schematic drawing showing a cross section in oneembodiment of the tire of the present invention, illustrating thearrangement of individual members of the tire of the present inventionsuch as a bead filler 7 and a side reinforcing rubber layer 8.

In FIG. 1, a suited embodiment of the tire of the present invention is atire provided with a carcass layer 2 which is ranged toroidally over aspace between a pair of bead cores 1, 1′ (1′ is not illustrated) andwhich comprises at least one radial carcass ply rolling up the abovebead core 1 from an inside of the tire to an outside thereof at both endparts, a side rubber layer 3 which is arranged at an outside of a tireaxial direction in a side region of the above carcass layer 2 to form anoutside part, a tread rubber layer 4 which is arranged at an outside ofa tire diameter direction in a crown region of the above carcass layer 2to form a grounding part, a belt layer 5 which is arranged between theabove tread rubber layer 4 and the crown region of the above carcasslayer 2 to form a reinforcing belt, an inner liner 6 which is arrangedon a whole surface of the carcass layer 2 at an inside of the tire toform an air proof film, a bead filler 7 which is arranged between a mainbody part of the carcass layer 2 extending from one bead core 1 to theother bead core 1′ and a roll-up part rolled up on the above bead core 1and at least one side reinforcing rubber layer 8 which is arrangedbetween the carcass layer 2 and the inner liner 6 from a bead filler 7side part to a shoulder zone 10 in a side region of the above carcasslayer and in which a cross-sectional form along a rotational axis of thetire is approximately lunate. By using at least one member selected fromthe group consisting of the side reinforcing rubber layer 8 and the beadfiller 7 using the rubber composition of the present invention, the tireof the present invention has improved run flat durability without damageto the ride comfort and the rolling resistance in normal running.

The carcass layer 2 of the tire of the present invention may comprise atleast one carcass ply or two or more carcass plies. The reinforcingcords of the carcass ply may be arranged at a substantially 90° to thecircumferential direction of the tire, with an embedded cord count of 35to 65 pieces/50 mm. Outside the crown region of the carcass 4 in theradial direction of the tire, a belt layer 5 comprising two layers of afirst belt layer 5 a and a second belt layer 5 b is arranged, though thenumber of layers in the belt layer 5 is not limited thereto. A pluralityof steel cords arranged in parallel in the width direction of the tirewithout twisting together may be embedded in rubber for use as the firstbelt layer 5 a and the second belt layer 5 b. For example, the firstbelt layer 5 a and the second belt layer 5 b may be arranged to crosseach other at the interlayer, so that a crossed belt can be formed.

Outside the belt layer 5 in the radial direction of the tire of thepresent invention, a belt reinforcing layer (not shown in drawing) maybe further arranged. The reinforcing cord of the belt reinforcing layeris preferably made from a high-modulus organic fiber to secure thetensile rigidity in the circumferential direction of the tire. Anorganic fiber cord of aromatic polyamide (aramid), polyethylenenaphthalate (PEN), polyethylene terephthalate, rayon, Zylon (registeredtrade mark) (polyp araphenylene benzobisoxazol (PBO) fiber), oraliphatic polyamide (nylon) may be used as the organic fiber cord.

In the tire of the present invention, reinforcing components such as aninsert and a flipper may be arranged besides the side reinforcing layer,though not shown in the drawing. The insert is a reinforcing materialusing a plurality of high-modulus organic fiber cords placed side byside and coated with rubber, so as to be arranged from the bead portion3 to the side portion 2 in the circumferential direction of the tire(not shown in drawing). The flipper is a reinforcing material made of aplurality of high-modulus organic fiber cords placed side by side andcoated with rubber, arranged between a main part of the carcass plyextending between the bead core 1 and 1′ and a turnup part around thebead core 1 or 1′, involving bead core 1 or 1′ and at least a part ofthe bead filler 7 arranged outside thereof in the radial direction ofthe tire. The angle of the insert and the flipper is preferably 30 to60° to the circumferential direction.

(Carcass Layer of Tire of the Present Invention)

Preferably, the tire of the present invention has, as a framework, acarcass layer comprising at least one carcass ply. In other words, thetire has, as a framework, a carcass layer comprising at least onecarcass ply. Preferably, a reinforcing cord of the carcass ply is anorganic fiber cord having an intermediate elongation of 4.2% or lessunder a load of 1.5 cN/dtex and a toughness of 45 cN·%/dtex or more, andthe tire is a tire having at least one member selected from the groupconsisting of a side reinforcing rubber layer and a bead filler usingthe rubber composition of the present invention.

The reason why a reinforcing cord of the carcass ply is preferably anorganic fiber cord having an intermediate elongation of 4.2% or lessunder a load of 1.5 cN/dtex and a toughness of 45 cN·%/dtex or more isas follows. The use of the reinforcing cord having a small dimensionalchange with an intermediate elongation of 4.2% or less can suppress theelongation of reinforcing cord caused by continuous strain of a tire inrunning, so that the durability and the steering stability of a tire canbe improved. Although a reinforcing cord is usually subjected to a diptreatment for improvement of the adhesion to rubber, the reinforcingcord having a high intermediate elongation are deteriorated in somecases due to cracks in the adhesive layer on the surface of thereinforcing cord caused by continuous strain of a tire in running.However, by using a reinforcing cord having a small intermediateelongation as the reinforcing cord of the carcass ply of a tire of thepresent invention, the deterioration of the adhesive layer caused bycontinuous strain of a tire in running can be prevented. Theintermediate elongation of the reinforcing cord of the carcass ply ispreferably 4.0% or less, more preferably 3.8% or less. The reinforcingcord referred to herein means a reinforcing cord before a tire ismanufactured.

Preferably, the reinforcing cord of the carcass ply removed from aproduct tire has an intermediate elongation of 6.0% or less under a loadof 1.5 cN/dtex. In particular, the intermediate elongation of thereinforcing cord at the part turned down from the bead core 1, or 1′ iscontrolled within the above range, so that excellence in both of theside cut resistance and the rigidity of a tire can be achieved.

The intermediate elongation is defined as an elongation (%) obtained inthe tension test in accordance with JIS L 1017: 2002, in which one cordsampled from the reinforcing cords after dip treatment is heated at 145°C. for 3 minutes under a tension of 1.5 cN/dtex and, after cooling,subjected to the test under a tensile load 1.5 cN/dtex under atemperature condition of 25±2° C. The toughness is defined as the areaunder the strain-stress curve (S-S curve) from the origin to thebreaking point of the reinforcing cord after dip treatment, the curvebeing obtained in the tension test under a temperature condition of25±2° C. The reinforcing cord of the carcass ply of a tire of thepresent invention made as described above allows the side cut resistanceand the steering stability to be balanced at a high level, and whenapplied to a run flat tire, excellent run flat durability can beobtained.

The tire of the present invention is a pneumatic tire which is suitablyused as a run flat tire.

Further, with a toughness of the reinforcing cord of the carcass ply ofa tire of the present invention of 45 cN·%/dtex or more, the steeringstability and the side cut resistance of the side portion 2 can beimproved at the same time. The toughness of the reinforcing cord is morepreferably 50 cN·%/dtex or more, and still more preferably 55 cN·%/dtexor more. It should be noted that the toughness of the reinforcing cordcan be adjusted by appropriately setting the type of dip solution, thedip temperature and dip time.

In the tire of the present invention, the reinforcing cord is subjectedto an adhesive treatment using an adhesive comprising at least oneselected from the group consisting of a thermoplastic polymer (A), athermal reaction-type aqueous urethane resin (B) and an epoxide compound(C) as a one-bath treatment liquid, and a resorcinol-formalin latexadhesive as a two-bath treatment liquid, and a main chain of thethermoplastic polymer (A) comprises at least one of an ethylenicaddition polymer and a urethane polymer having substantially nocarbon-carbon double bond having addition reactivity and mainly composedof a straight chain-structure, and has at least one cross-linkablefunctional group as a pendant group.

In particular, by compounding (B) and (C), the adhesion between thereinforcing cord and the rubber can be enhanced. Incidentally, althoughthe adhesion durability decreases under continuous strain as thestiffness increases, use of a reinforcing cord having a smallintermediate elongation as the reinforcing cord of the carcass ply of atire of the present invention suppresses the deformation amount of theentire cord as described above, so that the deterioration of theadhesive layer and the reduction in adhesive durability can beprevented. As an adhesive composition having the components (A) to (C)described above, the adhesive composition proposed in JP 4928661 B canbe used.

Examples of the ethylenically unsaturated monomer having onecarbon-carbon double bond as the monomer constituting the ethylenicaddition polymer of a thermoplastic polymer (A) include: α-olefins suchas ethylene, propylene, butylene, and isobutylene; α,β-unsaturatedaromatic monomers such as styrene, a-methylstyrene, monochlorostyrene,vinyltoluene, vinylnaphthalene, and styrene sodium sulfonate; ethyleniccarboxylic acids and salts thereof such as itaconic acid, fumaric acid,maleic acid, acrylic acid, methacrylic acid, and butene tricarboxylicacid; acid anhydrides such as maleic anhydride and itaconic anhydride;esters of unsaturated carboxylic acids such as methyl(meth)acrylate,ethyl(meth)acrylate, butyl(meth)acrylate, 2-ethylhexyl(meth)acrylate,polyethylene glycol methoxy(meth)acrylate, 2-hydroxyethyl(meth)acrylate,and 2-aminoethyl(meth)acrylate; monoesters of ethylenic dicarboxylicacids such as monoethyl itaconate, monobutyl fumarate, monobutylmaleate; diesters of ethylenical dicarboxylic acids such as diethylitaconate and dibutyl fumarate; amides of α,β-ethylenically unsaturatedacids such as acrylamide, maleic acid amide, N-methylol acrylamide,N-(2-hydroxyethyl)acrylamide, methacrylamide, N-methylol methacrylamide,N-(2-hydroxyethyl)methacrylamide, and maleic acid amide; hydroxylgroup-containing monomers such as 2-hydroxyethyl(meth)acrylate, andpolyethylene glycol mono(meth)acrylate; unsaturated nitriles such asacrylonitrile, methacrylonitrile, fumaronitrile, andα-chloroacrylonitrile; vinyl ethers such as methylvinyl ether andethylvinyl ether; vinyl ketones; vinyl amides; halogen-containingα,β-unsaturated monomers such as vinyl chloride, vinylidene chloride,vinyl fluoride, and vinylidene fluoride; vinyl compounds such as vinylacetate, vinyl valerate, vinyl caprylate, and vinyl pyridine; additionpolymerizable oxazolines such as 2-isopropenyl-2-oxazoline; heterocyclicvinyl compounds such as vinyl pyrrolidone; and unsaturatedbond-containing silane compounds such as vinyl ethoxy silane andα-methacryloxy propyltrimethoxy silane. These may be used alone or incombination of two or more. Preferably, the thermoplastic polymer (A) isobtained by the radical addition polymerization of these monomers.

Further, examples of the monomer containing two or more carbon-carbondouble bonds as monomer constituting the main chain skeleton includeconjugated diene based monomers such as 1,3-butadiene,2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, and ahalogen-substituted butadiene such as chloroprene. Examples of thenon-conjugated diene based monomer include vinyl norbornene,dicyclopentadiene, and 1,4-hexadiene, which may be used alone, or incombination of two or more.

Further, examples of the monomer containing two or more carbon-carbondouble bonds as monomer constituting the main chain skeleton includeconjugated diene based monomers such as 1,3-butadiene,2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, and ahalogen-substituted butadiene such as chloroprene. Examples of thenon-conjugated diene monomer include vinyl norbornene,dicyclopentadiene, and 1,4-hexadiene, which may be used alone, or incombination of two or more.

As the thermal reaction-type aqueous urethane resin (B), resins having aplurality of thermally dissociative blocked isocyanate groups in amolecule are preferably used. For example, thermal reaction-type aqueouspolyurethane compounds represented by the following general formula areoptimally used.

wherein A represents the isocyanate residue of an organic polyisocyanatecompound having 3 to 5 functional groups, Y represents the activehydrogen residue of a blocking agent compound which liberates anisocyanate group by heat treatment, Z represents the active hydrogenresidue of a compound having at least one active hydrogen atom and atleast one anion-forming group in a molecule, X is the active hydrogenresidue of a polyol compound having 2 to 4 hydroxyl groups and anaverage molecular weight of 5,000 or less, n is an integer of 2 to 4,and p+m is an integer of 2 to 4 (m≧0.25).

The epoxide compound (C) is preferably a compound containing epoxygroups or a reaction product of polyhydric alcohols and epichlorohydrin,though any compound having 2 or more, preferably 4 or more, epoxy groupsin a molecule can achieve the object of the present invention. Specificexamples of the epoxy compound include a reaction product of polyhydricalcohols and epichlorohydrin such as diethylene glycol diglycidyl ether,polyethylene diglycidyl ether, polypropylene glycol diglycidyl ether,neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether,glycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether,polyglycerol polyglycidyl ether, pentaerythiol polyglycidyl ether,diglycerol polyglycidyl ether, and sorbitol polyglycidyl ether; anovolac-type epoxy resin such as a phenol novolac-type epoxy resin and acresol novolac-type epoxy resin; and a bisphenol A-type epoxy resin. Asthe epoxide compound, sorbitol polyglycidyl ether or polyglycerolpolyglycidyl ether is preferably used.

In the present invention, a mixed liquid of the components (A), (B) and(C) described above is preferably used as the one-bath treatment liquid.The dry weight content of each of the components in the adhesivecomposition is preferably as follows: component (A): 2 to 75%, component(B): 15 to 87%, and component (C): 11 to 70%.

Further, in the tire of the present invention, the thermal shrinkagerate of the reinforcing cord after heat treatment is preferably 0.5 to3.0%. With a thermal shrinkage rate of the reinforcing cord of thecarcass ply in the above range, disarrangement of the position of thereinforcing cord due to thermal shrinkage in the period from tiremolding to vulcanization can be prevented. The rigidity of the tire,therefore, tends to be easily secured, so that the tire durability andthe steering stability can be stably obtained. Preferably, a rate of 1.0to 2.5% is preferred.

The thermal shrinkage rate is defined as a value obtained by dry heattreating a reinforcing cord after dip treatment under a load of 0.015g/dtex, at 177° C. for 2 minutes in an oven, measuring the code lengthbefore and after the heat treatment, and applying the followingExpression:

Heat shrinkage rate in dry heat treatment (%)={(Lb−La)/Lb}×100

In the Expression, La represents the code length after the heattreatment, and Lb represents the code length before heat treatment.

Preferably, the twist coefficient of the reinforcing cord of the carcassply of the tire of the present invention is 0.30 to 0.50, morepreferably 0.35 to 0.50. With a twist coefficient within the aboverange, the compression force applied to the reinforcing cord ismoderated, so that reduction in fatigue durability of the carcass plycan be prevented. Further, decrease in the tensile elastic modulus ofthe reinforcing cord can be prevented, so that the rigidity of a tirecan be sufficiently secured. In addition, a twist coefficient of thereinforcing cord of more than 0.50 is not preferred due to possiblereduction in the productivity of the cord in the twisting process. Thetwist coefficient T is expressed by the following Expression:

T=N×√{(0.125×D/2)/ρ}×10⁻³

wherein N is the number of second twist (turn/10 cm), D is the totalnominal decitex (fineness), ρ is the specific gravity of cord material.

Although any organic fiber cord having an intermediate elongation of4.2% or less under a load of 1.5 cN/dtex and a toughness of 45 cN·%/dtexor more can be used as the reinforcing cord of the carcass ply of a tireof the present invention, a cord made of polyester, particularly ofinexpensive polyethylene terephthalate (PET), is preferred. Knownstructures may be employed as the other structures of a tire.

The reinforcing cord of the carcass ply of a tire of the presentinvention can be suitably applied to a run flat tire having a sidereinforcing rubber layer arranged on the side portion.

The tire of the present invention has a pair of bead portions in whichbead cores 1 and 1′ are embedded respectively. A carcass layer 2 isturned down around the bead cores 1 and 1′ from the inside to theoutside of the tire so as to be engaged. The method for engaging thecarcass layer 2 is not limited thereto, though. For example, at leastone carcass ply of the carcass plies constituting the carcass layer 2,may be turned down around the bead cores 1 and 1′ from the inside towardthe outside in the tire width direction, so as to form a so-calledenvelope structure in which the turnup end is positioned between thebelt layer 5 and the crown portion of the carcass layer 2. Furthermore,a tread pattern may be appropriately formed on the surface of the treadrubber layer 4, and an inner liner 6 may be formed on the innermostlayer. The tire of the present invention may be filled with a gas suchas normal air or air with a partial oxygen pressure changed, or an inertgas such as nitrogen. The tire of the present invention is suitably usedas a pneumatic tire for passenger cars, particularly as a run flat tirefor passenger cars.

(Preparation of Rubber Composition, and Manufacturing of Tire)

The rubber composition of the present invention can be obtained bykneading the components according to the compounding recipe describedabove by a kneading machine such as a Banbury mixer, a roll, and aninternal mixer, and after subjected to mold processing, it is vulcanizedand used as at least one member selected from the group consisting ofthe side reinforcing rubber layer 8 and the bead filler 7 shown in FIG.1.

The tire of the present invention is manufactured by a conventionalmethod for manufacturing a run flat tire having at least one memberselected from the group consisting of a side reinforcing rubber layer 8and a bead filler 7 using the rubber composition of the presentinvention. That is, the rubber composition according to the presentinvention prepared by adding various chemicals in the manner describedabove is processed into the respective members in a non-vulcanizationstage, and the members are stuck and molded on a tire molding equipmentby a conventional method, whereby a green tire is molded. The abovegreen tire is heated and pressurized in a vulcanizing equipment toobtain a tire.

EXAMPLES

Next, the present invention shall be explained in further details withreference to examples, but the present invention shall by no means berestricted by the examples shown below.

The respective characteristics were measured according to the followingmethods.

<<Physical Properties of Modified Conjugate Diene Based Polymers>><Analytical Method of Micro Structure>

A content (% by mass) of the vinyl bond of a butadiene part was measuredby an infrared method Morello method).

<Measurements of Number Average Molecular Weight (Mn), Weight AverageMolecular Weight (Mw) and Molecular Weight Distribution (Mw/Mn)>

Measured by means of GPC (HLC-8020, manufactured by Tosoh Corp.) using arefractometer as a detector and shown in terms of polystyrene usingmonodispersed polystyrene as a standard. The column is GMHXL(manufactured by Tosoh Corp.), and the eluant is tetrahydrofuran.

<Measurement of Primary Amino Group Content (mmol/kg)>

First, the polymer was dissolved in toluene, and then it wasprecipitated in a large amount of methanol to separate an aminogroup-containing compound which was not bonded to the polymer from therubber, followed by drying it. The polymer subjected to the abovetreatment was used as a sample to quantitatively determine a whole aminogroup content thereof by “Testing method for total amine values”described in JIS K7237. Subsequently, the polymer subjected to thetreatment described above was used as a sample to quantitativelydetermine the contents of a secondary amino group and a tertiary aminogroup by “an acetylacetone blocked method”. o-Nitrotoluene was used forthe solvent dissolving the sample, and acetylacetone was added to carryout potentiometric titration by a perchloric acetic acid solution. Thecontents of a secondary amino group and a tertiary amino group werededucted from the whole amino group content to determine a primary aminogroup content (mmol), and it was divided by a mass of the polymer usedfor the analysis to thereby determine a content (mmol/kg) of a primaryamino group bonded to the polymer.

<<Evaluation of Pneumatic Tire>> <Run Flat Durability>

In Examples 1 to 20 and Comparative Examples 1 to 10, each of the samplerun flat tires (passenger car radial tires having a tire size of215/45ZR17) was rim-assembled under atmospheric pressure, charged to aninner pressure of 230 kPa, and then left standing in a room at 38° C.for 24 hours. Subsequently, the valve core was removed to obtain anatmospheric inner pressure for a running test on a drum under conditionsat a load of 4.17 kN (425 kg), a velocity of 89 km/h, and a roomtemperature of 38° C. The running distance until failure of each of thesample run flat tires was measured. The results were indicated by theindex based on the following Expression, with the running distance inComparative Example 1 as a reference of 100. As the index increases, thebetter run flat durability can be obtained. With an index of 125 ormore, improvement in the run flat durability is recognized, so that itcan be determined that the problem with the run flat durability, oneproblem of the present invention, was solved.

run flat durability (index)=(running distance of the test tire/runningdistance of the tire in Comparative Example 1)×100

In Examples 21 to 31, and Reference Examples 1 to 11, the air pressureof each tire 225/45R17 91Y(LI91=615 Kg) was set at 0 kPa (zero airpressure), and the tire mounted on a drum tester under a load of 4.5 kNwas subjected to running at 80 km/h. Based on the running distance untilfailure, the tire in Example 28 was rated as C (index: 100). A tirehaving a far longer running distance than that of Example 28 wasevaluated as extremely excellent and rated as A (index: 115 or more). Atire having a longer running distance than that of Example 28 wasevaluated as good and rated as B (index: 105 or more and less than 115).A tire having a running distance equivalent to that of Example 28 wasrated as C (index: more than 95 and less than 105). And a tire having arunning distance shorter than that of Example 28 was rated as D (index:95 or less). The results obtained are shown in Table 3. The rating C inTable 3 indicates excellent performance in the run flat durability, andthe ratings A and B indicate even better results.

Further, in the following Reference Examples 1 to 11, based on therunning distance until failure in the above test procedures, the tire inReference Example 1 was rated as c (index: 100). A tire having a farlonger running distance than that of Reference Example 1 was evaluatedas extremely excellent and rated as a (index: 115 or more). A tirehaving a longer running distance than that of Reference Example 1 wasevaluated as good and rated as b (index: 105 or more and less than 115).A tire having a running distance equivalent to that of Reference Example1 was rated as c (index: more than 95 and less than 105). And a tirehaving a running distance less than that of Reference Example 1 wasrated as d (index: 95 or less). The results obtained are shown in Table4.

However, the tire rated as C (index: 100) in Example 28, is superior tothe tire rated as c (index: 100) in Reference Example 1, having a farlonger running distance. The tires rated as B (index: 105 or more andless than 115) in Examples are vastly superior to the tires rated as b(index: 105 or more and less than 115) in Reference Examples 2 to 8.

<Ride Comfort>

In order to evaluate the ride comfort, the longitudinal spring constantof each of the sample run flat tires (passenger car radial tires havinga tire size of 215/45ZR17) rim-assembled at an air pressure of 230 kPawas measured under a load of 4.22 kN at normal temperature (25° C.). Thereciprocal of the longitudinal spring constant value of the run flattire in Comparative Example 1 was referred to as 100, and thelongitudinal spring constant values of the other run flat tires wereindicated by the indexes based on the following Expression. As the indexincreases, the longitudinal spring constant value decreases, which meansthat the better ride comfort can be obtained. With an index of 95 ormore, satisfactory ride comfort is recognized, so that it can bedetermined that the problem with the ride comfort, another problem ofthe present invention, was solved.

Ride comfort (index)=(longitudinal spring constant value in ComparativeExample 1/longitudinal spring constant value in sample tire)×100

<Side Cut Resistance>

The test of a tire 225/45R17 91Y(LI91=615 Kg) at an air pressure of 220kPa started under a load of 3.00 kN. In the test method, the sideportion of a rolling tire treads on a round pin-shaped jig fixed to thefloor. When no air leakage occurs after the test, the load applied tothe tire is increased to repeat the test. In the following Examples 21to 31, based on the load to cause air leakage in the above testprocedures, the tire in Example 28 was rated as C (index: 100). A tirehaving a far larger load to cause air leakage than that of Example 28was evaluated as extremely excellent and rated as A (index: 115 ormore). A tire having a larger load to cause air leakage than that ofExample 28 was evaluated as good and rated as B (index: 105 or more andless than 115). A tire having a load to cause air leakage equivalent tothat of Example 28 was rated as C (index: more than 95 and less than105). A tire having a load to cause air leakage smaller than that ofExample 28 was rated as D (index: more than 60 and 95 or less). And atire having a load to cause air leakage further smaller than that wasrated as E (index: 60 or less). The results obtained are shown in Table3. From the viewpoint of use as a tire, the evaluation results rated asA to D are preferred.

Further, in the following Reference Examples 1 to 11, based on the loadto cause air leakage in the above test procedures, the tire in ReferenceExample 1 was rated as c (index: 100). A tire having a far larger loadto cause air leakage than that of Reference Example 1 was evaluated asextremely excellent and rated as a (index: 115 or more). A tire having alarger load to cause air leakage than that of Reference Example 1 wasevaluated as good and rated as b (index: 105 or more and less than 115).A tire having a load to cause air leakage equivalent to that ofReference Example 1 was rated as c (index: more than 95 and less than105). And a tire having a smaller load to cause air leakage than that ofReference Example 1 was rated as d (index: 95 or less). The resultsobtained are shown in Table 4.

However, the tire rated as C (index: 100) in Example 28 is vastlysuperior to the tire rated as c (index: 100) in Reference Example 1. Thetires rated as B (index: 105 or more and less than 115) in Examples arevastly superior to the tires rated as b (index: 105 or more and lessthan 115) in Reference Examples 2 to 8.

<Steering Stability>

Each of the tires 225/45R17 91Y(LI91=615 Kg) at an air pressure of 230kPa was mounted on a dynamic tester under a load of 6.00 kN formeasurement of the cornering power (CP). In the following Examples 21 to31, based on the cornering power (CP) in the test procedures, the tirein Example 28 was rated as C (index: 100). A tire having a far largercornering power (CP) than that of Example 28 was evaluated as extremelyexcellent and rated as A (index: 115 or more). A tire having a largercornering power (CP) than that of Example 28 was evaluated as good andrated as B (index: 105 or more and less than 115). A tire having acornering power (CP) equivalent to that of Example 28 was rated as C(index: more than 95 and less than 105). A tire having a cornering power(CP) smaller than that of Example 28 was rated as D (index: more than 60and 95 or less). And a tire having a cornering power (CP) furthersmaller than that was rated as E (index: 60 or less). The resultsobtained are shown in Table 3. From the viewpoint of use as a tire, theevaluation results rated as A to D are preferred.

Further, in the following Reference Examples 1 to 13, based on thecornering power (CP) in the above test procedures, the tire in ReferenceExample 1 was rated as c (index: 100). A tire having a far largercornering power (CP) than that of Reference Example 1 was evaluated asextremely excellent and rated as a (index: 115 or more). A tire having alarger cornering power (CP) than that of Reference Example 1 wasevaluated as good and rated as b (index: 105 or more and less than 115).A tire having a cornering power (CP) equivalent to that of ReferenceExample 1 was rated as c (index: more than 95 and less than 105). And atire having a smaller cornering power (CP) than that of ReferenceExample 1 was rated as d (index: 95 or less). The results obtained areshown in Table 4.

However, the tire rated as C (index: 100) in Example 28 is vastlysuperior to the tire rated as c (index: 100) in Reference Example 1. Thetires rated as B (index: 105 or more and less than 115) in Examples arevastly superior to the tires rated as b (index: 105 or more and lessthan 115) in Reference Examples 2 to 8.

Manufacturing Example 1 Manufacturing of Modified Conjugated Diene BasedPolymer A (1) Manufacturing of Unmodified Polybutadiene

A 5 L autoclave substituted with nitrogen was charged with 1.4 kg ofcyclohexane, 250 g of 1,3-butadiene and 2,2-ditetrahydrofurylpropane(0.0285 mmol) in the form of a cyclohexane solution under nitrogen flow,and after 2.85 mmol of n-butyllithium (BuLi) was added thereto,polymerization was carried out for 4.5 hours in a warm water bath of 50°C. equipped with a stirring device. A reaction conversion rate of1,3-butadiene was almost 100%. A part of the above polymer solution wasput in a methanol solution containing 1.3 g of2,6-di-tert-butyl-p-cresol to terminate the polymerization, and then thesolvent was removed by steam stripping. The resulting solid matter wasdried on a roll of 110° C. to obtain polybutadiene before modification.The polybutadiene before modification thus obtained was used to measurea micro structure (vinyl bonding amount), a weight average molecularweight (Mw) and a molecular weight distribution (Mw/Mn). The resultsthereof showed a vinyl bonding amount of 14% by mass, Mw of 150,000 andMw/Mn of 1.1.

(2) Production of Primary Amine-Modified Polybutadiene A

The polymer solution obtained in (1) described above was maintained at atemperature of 50° C. without deactivating the polymerization catalyst,and 1129 mg (3.364 mmol) ofN,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane in which aprimary amino group was protected was added thereto to carry outmodification reaction for 15 minutes. Lastly, 2,6-di-tert-butyl-p-cresolwas added to the polymer solution after the reaction. Then, desolventand deprotection of the protected primary amino group were carried outby steam stripping, and the rubber was dried by a hot roll which wascontrolled at a temperature of 110° C. to obtain primary amine-modifiedpolybutadiene. The primary amine-modified polybutadiene thus obtainedwas used to measure a micro structure (vinyl bonding amount), a weightaverage molecular weight (Mw), a molecular weight distribution (Mw/Mn)and a primary amino group content. The results thereof showed a vinylbonding amount of 14% by mass, Mw of 150,000, Mw/Mn of 1.2 and a primaryamino group content of 4.0 mmol/kg.

Manufacturing Example 2 Manufacturing of Modified Conjugated Diene BasedPolymer B (3) Manufacturing of Secondary Amine-Modified Polybutadiene B

To the solution of unmodified polybutadiene obtained in “(1)Manufacturing of unmodified polybutadiene” in Manufacturing Example 1maintained at a temperature of 50° C. without deactivation ofpolymerization catalyst, 1,021 mg (3.364 mmol) ofN-(1,3-dimethylbutylidene)-3-(triethoxysilyl)-1-propane amine having aprotected secondary amino group was added to perform a modificationreaction for 15 minutes. At the end, 2,6-di-tert-butyl-p-cresol wasadded to the polymer solution after reaction. Subsequently, removal ofthe solvent and removal of the protection of the protected secondaryamino group were performed by steam stripping, and the rubber was driedby a heat roll controlled at a temperature of 110° C. so as to obtain asecondary amine-modified polybutadiene. The resulting modifiedpolybutadiene B was subjected to measurement of microstructure (vinylbond content), weight average molecular weight (Mw), and molecularweight distribution (Mw/Mn). The following results were obtained: avinyl bond content of 14% by mass, Mw of 150,000, and Mw/Mn of 1.2.

Manufacturing Example 3 Manufacturing of Modified Conjugated Diene BasedPolymer C (4) Manufacturing of SnCl₄-Modified Polybutadiene C

To the solution of unmodified polybutadiene obtained in “(1)Manufacturing of unmodified polybutadiene” in Manufacturing Example 1maintained at a temperature of 50° C. without deactivation ofpolymerization catalyst, 877 mg (3.364 mmol) of SnCl₄ was added toperform a modification reaction for 15 minutes. At the end,2,6-di-tert-butyl-p-cresol was added to the polymer solution afterreaction. Subsequently, removal of the solvent was performed by steamstripping, and the rubber was dried by a heat roll controlled at atemperature of 110° C. so as to obtain a SnCl₄-modified polybutadiene.The resulting modified polybutadiene C was subjected to measurement ofmicrostructure (vinyl bond content), weight average molecular weight(Mw), and molecular weight distribution (Mw/Mn). The following resultswere obtained: a vinyl bond content of 14% by mass, Mw of 150,000, andMw/Mn of 1.2.

Manufacturing Example 4 Manufacturing of Modified Conjugated Diene BasedPolymer D

An autoclave reactor having an inner volume of 5 liters purged withnitrogen was charged with 2,750 g of cyclohexane, 41.3 g oftetrahydrofuran, 125 g of styrene, and 375 g of 1,3-butadiene. After thetemperature of the reactor contents was adjusted to 10° C.,polymerization was initiated by the addition of 215 mg of n-butyllithium. The polymerization was performed under adiabatic conditions andthe maximum temperature reached 85° C.

When the polymerization conversion ratio reached 99%, 10 g of butadienewas added for further polymerization for 5 minutes. After sampling of asmall amount of the polymer solution in the reactor in 30 g of acyclohexane solution with addition of 1 g of methanol, 1,130 mg (3.366mmol) of N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane wasadded as modifier to perform a modification reaction for 15 minutes.Subsequently, 6.19 g of zirconium bis(2-ethylhexanoate)oxide ascondensation accelerator was added and stirred for further 15 minutes.At the end, 2,5-di-tert-butyl-p-cresol was added to the polymer solutionafter reaction. Subsequently, removal of the solvent was performed bysteam stripping, and the rubber was dried by a heat roll controlled at atemperature of 110° C. so as to obtain a modified conjugated diene basedpolymer D. The resulting modified conjugated diene based polymer D(modified styrene-butadiene copolymer) had a bonded styrene content of24.5% by mass and a vinyl bond content of 55% by mass.

Examples 1 to 20 and Comparative Examples 1 to 10

Thirty types of rubber compositions having 30 types of compoundingrecipes shown in Tables 1 and 2 were prepared. Using side reinforcingrubber layer 8 and the bead filler 7 shown in FIG. 1 using these 30types of rubber compositions, passenger car radial tires having a tiresize of 215/45ZR17 were manufactured, respectively, by the conventionalmethod. The run flat durability and the ride comfort of the respectivetires were evaluated. The results are shown in Tables 1 and 2. Themaximum thickness of the side reinforcing rubber layer of the tires wasset at 6.0 mm.

TABLE 1 Unit of compounding recipe: Example Parts by mass 1 2 3 4 5 6 78 9 10 Compounding Natural rubber *1 30.0 80.0 20.0 30.0 30.0 30.0 30.030.0 30.0 30.0 recipe Modified conjugated diene 70.0 20.0 80.0 0.0 0.00.0 70.0 70.0 70.0 70.0 of based polymer A *2 rubber Modified conjugateddiene 0.0 0.0 0.0 70.0 0.0 0.0 0.0 0.0 0.0 0.0 composition based polymerB *3 Modified conjugated diene 0.0 0.0 0.0 0.0 70.0 0.0 0.0 0.0 0.0 0.0based polymer C *4 Modified conjugated diene 0.0 0.0 0.0 0.0 0.0 70.00.0 0.0 0.0 0.0 based polymer D *5 Carbon black FEF (B) *6 60.0 60.060.0 60.0 60.0 60.0 60.0 80.0 60.0 60.0 Phenol resin F (C) *7 0.0 0.00.0 0.0 0.0 0.0 1.2 0.0 0.0 0.0 Cashew-modified phenol 1.2 1.2 1.2 1.21.2 1.2 0.0 1.2 1.0 2.0 resin (C) *8 Hexamethylenetetramine 0.12 0.120.12 0.12 0.12 0.12 0.12 0.12 0.12 0.12 (D) *9 Thiuram based 1.8 1.8 1.81.8 1.8 1.8 1.8 1.8 1.8 1.8 vulcanization accelerating agent TOT (E) *10Thiuram based 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 vulcanizationaccelerating agent TET (E) *11 Sulfenamide based 3.3 3.3 3.3 3.3 3.3 3.33.3 3.3 3.3 3.3 vulcanization accelerating agent (F) *12 Antioxidant *131.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 Sulfur 5.5 5.5 5.5 5.5 5.5 5.55.5 5.5 5.5 5.5 (E)/(F) 0.55 0.55 0.55 0.55 0.55 0.55 0.55 0.55 0.550.55 [(C)/(B)] × 100 2.0 2.0 2.0 2.0 2.0 2.0 2.0 1.5 1.7 3.3 Run flatdurability index 149 136 130 133 133 133 140 133 145 161 Ride comfortindex 100 98 100 100 100 100 100 97 100 95 Unit of compounding recipe:Example Parts by mass 11 12 13 14 15 16 17 18 19 20 Compounding Naturalrubber *1 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 recipeModified conjugated diene 70.0 70.0 70.0 70.0 70.0 70.0 70.0 70.0 70.070.0 of based polymer A *2 rubber Modified conjugated diene 0.0 0.0 0.00.0 0.0 0.0 0.0 0.0 0.0 0.0 composition based polymer B *3 Modifiedconjugated diene 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 based polymer C*4 Modified conjugated diene 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0based polymer D *5 Carbon black FEF (B) *6 60.0 60.0 60.0 60.0 60.0 60.060.0 60.0 100.0 60.0 Phenol resin F (C) *7 0.0 0.0 0.0 0.0 0.0 0.0 0.00.0 0.0 0.0 Cashew-modified phenol 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 0.92.4 resin (C) *8 Hexamethylenetetramine 0.18 0.12 0.12 0.12 0.12 0.120.12 0.12 0.12 0.12 (D) *9 Thiuram based 1.8 1.5 2.0 0.0 1.8 1.8 1.8 2.11.8 1.8 vulcanization accelerating agent TOT (E) *10 Thiuram based 0.00.0 0.0 1.8 0.0 0.0 0.0 0.0 0.0 0.0 vulcanization accelerating agent TET(E) *11 Sulfenamide based 3.3 3.3 3.3 3.3 3.2 4.3 4.5 3.3 3.3 3.3vulcanization accelerating agent (F) *12 Antioxidant *13 1.0 1.0 1.0 1.01.0 1.0 1.0 1.0 1.0 1.0 Sulfur 5.5 5.5 5.5 5.5 5.5 5.5 5.5 5.5 5.5 5.5(E)/(F) 0.55 0.45 0.61 0.55 0.56 0.42 0.40 0.64 0.55 0.55 [(C)/(B)] ×100 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 0.9 4.0 Run flat durability index157 137 153 138 145 135 138 153 130 135 Ride comfort index 97 101 98 100102 98 97 98 95 96

TABLE 2 Unit of compounding recipe: Comparative Example Parts by mass 12 3 4 5 6 7 8 9 10 Compounding Natural rubber *1 30.0 90.0 10.0 30.030.0 30.0 30.0 30.0 30.0 30.0 recipe Modified conjugated diene 70.0 10.090.0 70.0 70.0 70.0 70.0 70.0 70.0 70.0 of based polymer A *2 rubberModified conjugated diene 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0composition based polymer B *3 Modified conjugated diene 0.0 0.0 0.0 0.00.0 0.0 0.0 0.0 0.0 0.0 based polymer C *4 Modified conjugated diene 0.00.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 based polymer D *5 Carbon black FEF(B) FEF *6 60.0 60.0 60.0 55.0 105.0 60.0 60.0 60.0 60.0 60.0 Phenolresin F (C) F *7 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Cashew-modifiedphenol 2.5 1.2 1.2 1.2 1.2 0.5 2.5 1.2 1.2 1.2 resin (C) *8Hexamethylenetetramine 1.20 0.12 0.12 0.12 0.12 0.12 0.12 0.12 0.12 0.12(D) *9 Thiuram based vulcanization 1.0 1.8 1.8 1.8 1.8 1.8 1.8 1.3 1.81.8 accelerating agent TOT (E) *10 Thiuram based vulcanization 0.0 0.00.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 accelerating agent TET (E) *11Sulfenamide based vulcanization 3.0 3.3 3.3 3.3 3.3 3.3 3.3 3.3 3.0 4.7accelerating agent (F) *12 Antioxidant *13 1.0 1.0 1.0 1.0 1.0 1.0 1.01.0 1.0 1.0 Sulfur 5.5 5.5 5.5 5.5 5.5 5.5 5.5 5.5 5.5 5.5 (E)/(F) 0.330.55 0.55 0.55 0.55 0.55 0.55 0.39 0.60 0.38 [(C)/(B)] × 100 4.2 2.0 2.02.2 1.1 0.83 4.2 2.0 2.0 2.0 Run flat durability index 100 120 113 122124 116 128 100 123 126 Ride comfort index 100 97 100 101 90 103 91 103105 93

[Note]

-   *1. Natural rubber: RSS #1-   *2. Modified conjugated diene based polymer A: modified conjugated    diene based polymer obtained in Manufacturing Example 1 (modified    polybutadiene)-   *3. Modified conjugated diene based polymer B: modified conjugated    diene based polymer obtained in Manufacturing Example 2 (modified    polybutadiene)-   *4. Modified conjugated diene based polymer C: modified conjugated    diene based polymer obtained in Manufacturing Example 3 (modified    polybutadiene)-   *5. Modified conjugated diene based polymer D: modified conjugated    diene based polymer obtained in Manufacturing Example 4 (modified    styrene-butadiene copolymer)-   *6. Carbon black FEF: N550, manufactured by Asahi Carbon Co., Ltd.,    trade name: “ASAHI #60”-   *7. Phenol resin F: straight (unmodified) phenol resin, manufactured    by Sumitomo Bakelite Co., Ltd., trade name: “SUMILITERESIN PR-50731”-   *8. Cashew-modified phenol resin: manufactured by Sumitomo Bakelite    Co., Ltd., trade name: “SUMILITERESIN PR-BSN-21”-   *9. Hexamethylenetetramine: manufactured by Wako Pure Chemical    Industries, Ltd.-   *10. Vulcanization accelerating agent TOT:    tetrakis(2-ethylhexyl)thiuram disulfide, manufactured by Ouchi    Shinko Chemical Industrial Co., Ltd., trade name: “NOCCELER TOT-N”-   *11. Vulcanization accelerating agent TET: tetraethylthiuram    disulfide, manufactured by Ouchi Shinko Chemical Industrial Co.,    Ltd., trade name: “NOCCELER TET-G”-   *12. Vulcanization accelerating agent NS:    N-(tert-butyl)-2-benzothiazolyl sulfenamide, manufactured by Sanshin    Chemical Industry Co., Ltd., trade name: “SANCELER NS-G”-   *13. Antioxidant 6C:    N-(1,3-dimethylbutyl)-NP-phenyl-p-phenylenediamine, manufactured by    Ouchi Shinko Chemical Industrial Co., Ltd., trade name: “NOCRAC 6C”

As is apparent from Tables 1 and 2, all of the tires having a sidereinforcing rubber layer 8 and a bead filler 7 shown in FIG. 1 using anyof the rubber compositions in Examples 1 to 20 can have both of a runflat durability index of 125 or more and a ride comfort index of 95 ormore in parallel, being capable of solving the problem of the presentinvention.

On the other hand, all of the tires having a side reinforcing rubberlayer 8 and a bead filler 7 shown in FIG. 1 using any of the rubbercompositions in Comparative Examples 1 to 10 cannot have both of a runflat durability index of 125 or more and a ride comfort index of 95 ormore in parallel, being incapable of solving the problem of the presentinvention.

Examples 21 to 31 and Reference Examples 1 to 11

In the same manner as in Examples 1 to 20 and Comparative Examples 1 to10, 22 types of passenger car radial run flat tires having a tire sizeof 225/45R17 91Y(LI91=615 Kg) were manufactured by the conventionalmethod for evaluation of the run flat durability, the side cutresistance, and the steering stability. The following adhesive A wasused as an adhesive in all of the cases. The physical properties of thereinforcing cords of the carcass ply and the evaluation results areshown in Tables 3 and 4.

<Adhesive A>

The dip solution of the first bath is A-1 comprising 16.5% by mass(weight of solid content) of EPOCROS K1010E (manufactured by NipponShokubai Co., Ltd., oxazoline-containing polymer), 6% by mass (weight ofsolid content) of ELASTRON BN27 (manufactured by Daiichi Kogyo SeiyakuCo., Ltd., water-based urethane resin), 7.5% by mass (weight of solidcontent) of DENACOL EX614B (manufactured by Nagase Kasei Kogyo Co.,Ltd., multi-functional-type (4 or more functional groups) aliphaticepoxy resin), and 70% by mass of water. The dip solution of the secondbath is A-2 comprising 524.01 parts by mass of water, 15.12 parts bymass of resorcinol, 16.72 parts by mass of formalin (37%), 4.00 parts bymass of caustic soda (10%), 233.15 parts by mass ofvinylpyridine-styrene-butadiene copolymer latex (JSR0655, manufacturedby JSR Corporation, solid content concentration: 41%), and 207.00 partsby mass of styrene-butadiene copolymer latex (JSR2108, manufactured byJSR Corporation, solid content concentration: 40%).

The carcass ply cords in Examples 21 to 31 and Reference Examples 1 to11 were made of a multi-filament organic fiber including two multi-yarnbundles twisted to make a first twist and a second twist. The twistedcord of the organic fiber was immersed in a one-bath treatment liquid,and treated in a dry zone at 160° C. under a tension of 0.6 g/dtex for60 seconds and in a hot zone at 240° C. under a tension of 0.6 g/dtexfor 60 seconds. Subsequently, the cord was immersed again in a two-bathtreatment liquid of resorcinol-formalin latex (RFL) based adhesive undera dip tension of 200 g, and treated again in a dry zone at 180° C. undera tension of 0.6 g/dtex for 60 seconds and in a hot zone for 60 seconds.The cord was thus subjected to heat treatment for 240 seconds in total,so as to be coated with the adhesive. In the hot zone of the final diptreatment, the temperature was finely adjusted in the range from 240° C.to 250° C. and the tension was finely adjusted in the range from 0.2 to0.5 g/dtex, so that the intermediate elongation was adjusted.

In Tables 3 and 4, PET represents a polyethylene terephthalate fiber. Apara-aramid fiber (KEVLAR (registered trademark) manufactured by DuPont-Toray Co., Ltd.) was used as aramid.

TABLE 3 Example 21 22 23 24 25 26 27 28 29 30 31 Type of cord PET PETPET PET PET PET PET Aramid PET PET PET Fineness (dtex/ply) 1670/2 1670/21670/2 2200/2 2200/2 3340/2 3340/2 1670/2 2200/2 1670/2 1670/2Intermediate elongation 4.1 3.7 4.2 3.0 3.5 3.8 3.2 0.85 4.4 3.6 5.2 (%)after heat treatment Toughness (cN %/dtex) 48 51 60 56 58 82 65 29 42 3860 Thermal shrinkage rate (%) 1.9 1.6 1.5 2.3 1.3 1.7 1.3 0.0 3.6 2.64.2 Twist coefficient 0.48 0.48 0.48 0.45 0.45 0.40 0.36 0.50 0.48 0.480.48 Rubber composition for use Rubber composition in Example 1 in sidereinforcing rubber layer and bead filler Side cut resistance A A A A A AA C D D B Steering stability A A A A A A A C D B D Run flat durability AA A A A A A C B B B

TABLE 4 Reference Example 1 2 3 4 5 6 7 8 9 10 11 Type of cord AramidPET PET PET PET PET PET PET PET PET PET Fineness (dtex/ply) 1670/21670/2 1670/2 1670/2 2200/2 2200/2 3340/2 3340/2 2200/2 1670/2 1670/2Intermediate elongation (%) after heat 0.85 4.1 3.7 4.2 3.0 3.5 3.8 3.24.4 3.6 5.2 treatment Toughness (cN %/dtex) 29 48 51 60 56 58 82 65 4238 60 Thermal shrinkage rate (%) 0.0 1.9 1.6 1.5 2.3 1.3 1.7 1.3 3.6 2.64.2 Twist coefficient 0.50 0.48 0.48 0.48 0.45 0.45 0.40 0.36 0.48 0.480.48 Rubber composition for use in side Rubber composition inComparative Example 1 reinforcing rubber layer and bead filler Side cutresistance c b b b b b b b d d b Steering stability c b b b b b b b d bd Run flat durability c b b b b b b b d b d

From Table 3, it can be seen that the tire and the run-flat tire, inparticular, of the present invention exhibit excellent results in therun flat durability, with great improvement in the side cut resistanceand the steering stability, which are balanced at a high level.

In particular, as is apparent from Table 3, the pneumatic tires(Examples 21 to 27) having a side reinforcing rubber layer and a beadfiller using the rubber composition of the present invention, using anorganic fiber cord having an intermediate elongation at a load of 1.5cN/dtex of 4.2% or less and a toughness of 45 cN·%/dtex or more as areinforcing cord of the carcass ply are superior in all of the run flatdurability, the side cut resistance, and the steering stability than thepneumatic tires (Examples 28 to 31) having a side reinforcing rubberlayer and a bead filler using the rubber composition of the presentinvention, using an organic fiber cord not satisfying one of anintermediate elongation at a load of 1.5 cN/dtex of 4.2% or less and atoughness of 45 cN·%/dtex or more as a reinforcing cord of the carcassply.

In other words, the pneumatic tires in Examples 21 to 27 obtain aremarkable synergistic effect of having a side reinforcing rubber layerand a bead filler using the rubber composition of the present inventionand using an organic fiber cord having an intermediate elongation at aload of 1.5 cN/dtex of 4.2% or less and a toughness of 45 cN·%/dtex ormore as a reinforcing cord of the carcass ply, in comparison with thepneumatic tires in Examples 28 to 31.

On the other hand, as is apparent from Table 4, it is recognized thatthe pneumatic tires (Reference Examples 2 to 8) having a sidereinforcing rubber layer and a bead filler using the rubber compositionin Comparative Example 1, using an organic fiber cord having anintermediate elongation at a load of 1.5 cN/dtex of 4.2% or less and atoughness of 45 cN·%/dtex or more as a reinforcing cord of the carcassply are superior in any one of the run flat durability, the side cutresistance, and the steering stability than the pneumatic tires(Reference Examples 1 and 9 to 11) having a side reinforcing rubberlayer and a bead filler using the rubber composition in ComparativeExample 1, using an organic fiber cord not satisfying one of anintermediate elongation at a load of 1.5 cN/dtex of 4.2% or less and atoughness of 45 cN·%/dtex or more as a reinforcing cord of the carcassply.

However, the remarkable synergistic effect obtained in the pneumatictires in Examples 21 to 27 is not exhibited in the pneumatic tires inReference Examples 2 to 8 in comparison with the pneumatic tires inReference Examples 1 and 9 to 11. In other words, the pneumatic tires inExamples 21 to 27 can exhibit the remarkable synergistic effect only dueto the combination of the rubber composition of the present inventionand the reinforcing cord of the carcass ply of the present invention.

The pneumatic tires in Examples 21 to 27 are vastly superior in all ofthe run flat durability, the side cut resistance, and the steeringstability than the pneumatic tires in Reference Examples 2 to 8.

INDUSTRIAL APPLICABILITY

The rubber composition of the present invention allows the ride comfortof a run flat tire in normal running to be satisfied in parallel withimprovement in the run flat durability (durability in run flat running).Further, using an organic fiber cord having a specific intermediateelongation and a specific toughness as a reinforcing cord of the carcassply, the run flat durability is excellent as well as the side cutresistance and the steering stability are also improved, and thus thetire can be suitably used as a run flat tire.

REFERENCE SIGNS LIST

-   1, 1′ Bead cores-   2 Carcass layer-   3 Side rubber layer-   4 Tread rubber layer-   5 Belt layer-   6 Inner liner-   7 Bead filler-   8 Side reinforcing rubber layer-   10 Shoulder zone

1. A rubber composition prepared by mixing 60 to 100 parts by mass of afiller (B), 0.9 to 2.4 parts by mass of a phenol resin (C), 0.07 to 0.2parts by mass of a methylene donor (D), 1.5 to 2.1 parts by mass of athiuram based vulcanization accelerating agent (E), and 3.2 to 4.5 partsby mass of a sulfenamide based vulcanization accelerating agent (F),based on 100 parts by mass of a rubber component comprising 20 to 80% bymass of a modified conjugated diene based polymer (A).
 2. The rubbercomposition according to claim 1, wherein the amounts of the thiurambased vulcanization accelerating agent (E) and the sulfenamide basedvulcanization accelerating agent (F) mixed satisfy the followingExpression (I):0.45≦mass ratio [amount of thiuram based vulcanization acceleratingagent (E) mixed/amount of sulfenamide based vulcanization acceleratingagent (F) mixed]≦0.65   (I)
 3. The rubber composition according to claim1, wherein the amounts of the filler (B) and the phenol resin (C) mixedsatisfy the following Expression (II):1.0≦[mass ratio {amount of phenol resin (C) mixed/amount of carbon blackmixed}]×100≦4.0   (II)
 4. The rubber composition according to claim 1,wherein the modified conjugated diene based polymer is an amine-modifiedpolybutadiene.
 5. The rubber composition according to claim 1, whereinthe filler (B) is carbon black.
 6. A tire comprising at least one memberselected from the group consisting of a side reinforcing rubber layerand a bead filler using the rubber composition according to claim
 1. 7.The tire according to claim 6, wherein the tire has, as a framework, acarcass layer comprising at least one carcass ply, a reinforcing cord ofthe carcass ply being an organic fiber cord having an intermediateelongation of 4.2% or less under a load of 1.5 cN/dtex and a toughnessof 45 cN·%/dtex or more.
 8. The tire according to claim 7, wherein thereinforcing cord is subjected to an adhesive treatment using an adhesivecomprising at least one selected from the group consisting of athermoplastic polymer (A), a thermal reaction-type aqueous urethaneresin (B) and an epoxide compound (C) as a one-bath treatment liquid,and a resorcinol-formalin latex adhesive as a two-bath treatment liquid,and a main chain of the thermoplastic polymer (A) comprises at least oneof an ethylenic addition polymer and a urethane polymer havingsubstantially no carbon-carbon double bond having addition reactivityand mainly composed of a straight chain-structure, and has at least onecross-linkable functional group as a pendant group.
 9. The tireaccording to claim 7, wherein the reinforcing cord has a thermalshrinkage rate after heat treatment of 0.5 to 3.0%.
 10. The tireaccording to claim 7, wherein the reinforcing cord removed from the tirehas an intermediate elongation of 6.0% or less under a load of 1.5cN/dtex.
 11. The tire according to claim 7, wherein the reinforcing cordhas a twist coefficient of 0.35 to 0.50.
 12. The tire according to claim7, wherein the reinforcing cord is made of polyethylene terephthalate.